Abstract
In order to detect structural changes of the CK molecule due to bound substrates, the dynamics of free, ATP-bound, and ATP + creatine-bound CK were examined, using steady-state and time-resolved fluorescence spectroscopy. The intrinsic tryptophan fluorescence of non-labelled CK presented the smaller fluorescence lifetime 2.38 ns and rotation correlation time 27 ns for the CK-ATP (in comparison with the times 2.72 ns and 35 ns for the free CK), and their moderate return to the longer times 2.42 ns and 29 ns for the CK-ATP + creatine complex.
Data were confirmed by anisotropy experiments with CK-(FITC labelled), providing the same substrate dependence of the rotation times (34 ns, 27 ns and returning 30 ns). The results indicate the existence of three conformations arranged according to the "energy minimizing principle" by ligated substrates.